1. Technical Field
The present invention relates to a technique for restricting use of content stored in a communication terminal device.
2. Background Information
There are now in wide-spread use mobile phones that have a browsing capability and that are able to download and store programs, sound and image data (hereinafter, content) from a WWW (World Wide Web) server on the Internet. Subject to agreement and payment of a fee, as necessary, a user of such a phone is able to download, store and own desired content. Such a mobile phone used by the user to download, store and own such content is used to execute a program to enable content to be utilized, and also has output sound means to output sound of content, and display means for displaying content.
A technique has been proposed in the art where a management device stores content that is the same as that owned by a user, which management device is capable of communicating with the user's mobile phone, such that content owned by a user is updated when content stored in the management device is updated. For example, a technique disclosed in Japanese Patent Application Laid-Open Publication No. 11-25017 (hereinafter, JP 11-25017) provides a management device for storing a destination registration table in which a phone number of a user's mobile phone is stored, and for transmitting a message requesting a mobile phone whose phone number is registered in the destination registration table to update content when corresponding content stored in the management device is updated. A mobile phone, when receiving the message, updates content stored in the phone based on details of the message. Content stored in a mobile phone is thus updated when corresponding content stored in a management device is update.
However, content stored or updated in a mobile phone may expire or be subject to unauthorized use. Also, a user may no longer wish to use content stored in his/her mobile phone and may wish to cancel a usage contract which authorizes use of the content. In such a case, a management device of the same type as the above may be used to store correspondence information, with a record in the correspondence information showing correspondence between a user and content owned by the user. Accordingly, when a record of content used by a user is deleted from the correspondence information stored in the management device, content to be deleted from a user's mobile phone is identified on the basis of the deleted record. Conversely, in a case that a user deletes content from a phone, the management device can be caused to delete a record of the content from the stored correspondence information. By using such a system a content provider, hereinafter, a CP (content provider), is able to prevent unauthorized use of content by deleting a record of content from correspondence information stored in a management device, when such a record is deemed to have expired or to be subject to unauthorized, for example unpaid, use. As stated above, the converse also applies in that a user is able to delete content stored in his/her mobile phone, thereby prompting deletion of the content record at the management device side and avoiding the need for time consuming cancellation of a contract using documentation.
A new type of a mobile phone has recently been proposed, having mounted thereto a removable User Identity Module (hereinafter, UIM) containing an identifier such as a user's phone number for uniquely identifying a user on a communication network. A user is able to use different mobile phones with a single phone number by mounting a UIM to a mobile phone as required. For example, a UIM may be switched between a mobile phone used for storing business-related content and a mobile phone for private use for storing content such as game programs depending on the circumstances of the user.
A problem arises, however, in a case where more than one mobile phones is being used by a user by way of a UIM and content stored in one of the mobile phones (first mobile phone) is no longer authorized for use by the user, if the content stored in the first mobile phone is caused to be deleted by the above-mentioned management device. Namely, a management device transmits a message requesting a mobile phone to delete the content, specifying the destination of the message with a user's phone number, and the request is received by a mobile phone having mounted a UIM which contains information of the destination phone number at the time of receiving the request. However, the receiving mobile phone may not necessarily be the mobile phone storing the content corresponding to the deleted content record (first mobile phone) but may be a different mobile phone (second mobile phone) in which no such content is stored. As will be apparent, in such a case, the content at issue is not deleted if the request is received by the second mobile phone. Moreover, a further case can be readily envisaged wherein the second mobile phone is not owned by the same user as the one who owns the first mobile phone, and the same content, this case, authorized, as that stored in the first mobile phone is stored in the second mobile phone. In such a case, the second mobile phone is caused to delete the content, even though its use is authorized for a legitimate user, as a result of receipt at the phone of a request to delete the content. Consequently, a CP is thus not able to reliably prevent unauthorized use of content when a single UIM is used for different mobile phones storing content.